Complexes coordination chemistry concepts

Kawagudi, S. Variety of Coordination Modes of Ligands in Metal Complexes. Inorganic Chemistry Concepts. Springer-Verlag Chemie Berlin, 1988, vol. 11. 

Kawaguchi, Shinichi, 1920-Variety in coordination modes of ligands in metal complexes. (Inorganic chemistry concepts) Bibliography p. Includes index. 1. Complex compounds. 2. Chemical bonds. 3. Ligands. I. Title. II. Series. 

In the sixties of past century, a few patents issued to Bergbau Chemie [5,48,49] and to Mobil Oil [50-52], respectively described the use of CFPs as supports for catalytically active metal nanoclusters and as carriers for heterogenized metal complexes of catalytic relevance. For the latter catalysts the term hybrid phase catalysts later came into use [53,54], At that time coordination chemistry and organo-transition metal chemistry were in full development. Homogeneous transition metal catalysis was expected to grow in industrial relevance [54], but catalyst separation was generally a major problem for continuous processing. That is why the concept of hybrid catalysis became very popular in a short time [55]. 

Metal Ion Adsorption in Mixtures of Multiple Solid Phases. One of the arguments put forth for extending the concepts of solution coordination chemistry to heterogeneous systems is the hypothesis that the mineral components of soils or sediments can be considered as ligands which compete for complexation of adsorbates. To this end, it is important to know the relative ability of different mineral surfaces to complex solutes. 

The preparation of stable complexes with transition metal-phosphorus triple bonds is of fundamental importance and constitutes a novel field of coordination chemistry. The contribution of B.P. Johnson, G. Balazs, and M. Scheer reports the synthesis and isolation of such complexes for transition metals in high oxidation states in contrast, the corresponding complexes with transition metals in low oxidation states were found to exist only as highly reactive intermediates. A synthetic concept to generate directly such intermediates is documented. The present knowledge of the reactivity pattern of all these types of compounds is summarized in chapter 1. 

Werner s coordination theory25 was a watershed in the history of coordination chemistry and gave the field its name. With a few exceptions, the majority of chemists accepted Werner s views, and most 20th century contributions have been developments, extensions or confirmations of Werner s theory rather than ideas incompatible with or opposed to it. Ley s concept of inner complex salts is one of the earliest of such post-Werner developments.80... 

Historically, the concept of coordination chemistry was associated with complexation of a metal cation (Lewis acid) by a ligand behaving as a Lewis base. Such was traditionally the case for macrocyclic molecules as ligands. In the early 1970s, however, the concept of coordination chemistry was extended in the area of macrocyclic chemistry to include molecular cations, neutral molecules and anions as substrates. Complexes of all of these species are to be included in the scope of this chapter section. Examples of the types of substrates are discussed below. 

Photochemistry as a science is quite young we only need to go back less than one century to find its early pioneer [1], The concept of coordination compound is also relatively young it was established in 1892, when Alfred Werner conceived his theory of metal complexes [2]. Since then, the terms coordination compound and metal complex have been used as synonyms, even if in the last 30 years, coordination chemistry has extended its scope to the binding of all kinds of substrates [3,4],... 

This chapter has presented an overview of several important aspects of the chemistry of coordination compounds. In addition to the elementary ideas related to bonding presented here, there is an extensive application of molecular orbital concepts to coordination chemistry. However, most aspects of the chemistry of coordination compounds treated in this book do not require this approach, so it is left to more advanced texts. The references at the end of this chapter should be consulted for more details on bonding in complexes. 

The parent ligand has played an important part in the history of coordination chemistry, as the stereochemical arrangement of bidentate bis or tris (en) complexes lead to the concept of... 

The crystal structures of numerous other complexes of various coordination numbers have been determined, completely and directly confirming Werner s earlier indirect configurational proofs by the preparation of isomers and resolution of optically active compounds (see Section 4). Today, the terminology and concepts of coordination chemistry are universally used in crystallography. 

Central to the stability and chemistry of complexes formed by mixed donor ligands are two key concepts of coordination chemistry. The first is the chelate effect, which applies to all polydentate ligands, and reflects the increase in stability of a type of complex as monodentate donor molecnles are replaced by polydentates with donors linked by chelate rings. The hard-soft acid-base theory is particnlarly relevant to mixed donor ligands where donors of distinctly different character may bind to a central metal ion. The like prefers like concept means hard nonpolarizable donor atoms (N and O, for example) bond preferentially to hard nonpolarizable metal... 

Platinum is found in compounds having a smaller range of oxidation states than is the case for many of the earlier elements in the periodic table. The differences between it and Pd are somewhat more marked than for analogous pairs of earlier elements. The coordination numbers see Coordination Numbers Geometries) tend to be lower than for earlier elements a CN of six is rarely exceeded and a CN of four is common. Many important concepts in coordination chemistry, such as square-planar coordination and the trans effect, were first discovered in Pt complexes. The high electronegativity of the element is reflected in a poor 7t-basic character, which helps account for the lack of a binary carbonyl. 

---